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SEEDS
The terrestrial plants used in the FOSS program are varieties
that have been developed as food sources for humans and the animals
humans raise: alfalfa (a legume), barley, corn, bean, pea, clover,
radish, rye grass, wheat, oats, and sunflower. Students encounter
them as seeds and grow them in a variety of environments. As mundane
as these seeds are, they hold the most powerful message on earth:
each can develop into a living replica of its progenitor from
the genetic message carried in a single cell.
Seeds carry a tiny embryo of the new plant, and a food supply
that will nourish and fuel the first few days of life. The two
pulpy halves of the bean store the food for the seedling, and
it is these same food sources that we use for food when we eat
beans. These food storage units, the cotyledons, are found on
every seed. Sometimes they are tiny, as in clover seeds, and sometimes
they look strange, as in the wrinkly meat of the walnut, but the
function is always the same. Plants that have two cotyledons are
classified as dicots.
Far more important in terms of their contribution to feeding
the world's population of humans are the plants that have only
one cotyledon, the monocots. These include grasses, among others;
all grains are grasses. The most important food plant is rice,
followed by wheat, corn, and barley.
It must be remembered that seeds are living organisms in a dormant
stage. Most seeds are capable of resting in this dormant stage
for extended periods: 2 or 3 years for most plants, but up to
several decades for others. When conditions of moisture and temperature
are right, germination, or sprouting, occurs. The seed is capable
of growth and development for several days in complete darkness,
but after the energy from the cotyledon is exhausted, it must
have light or it will starve to death. In the presence of light
it can make its own food by photosynthesis.
In the classroom students will be anxious to plant seeds in order
to observe one of the miracles of the world. They may not know
how to plant, however, and they will need guidance from you. The
general rule is that the smaller the seed, the shallower it is
placed in the soil. Tiny seeds like clover can simply be spread
on the surface of the soil. Large seeds like corn and peas, however,
should be planted up to 1 cm (1/2") deep.
Students often overwater their plants in their eagerness to take
good care of them. One of the lessons learned in the Environments
Module is that too much of a good thing can be as lethal
as too little. The general rule for watering is to water when
the surface of the soil looks and feels dry, and then only enough
to moisten the soil, not to soak it.
Students may ask which side of the seed is up. It really doesn't
matter much because seeds are programmed so that the root goes
down when it emerges from the seed and the shoot goes up.
What to do when the seeds arrive. It's a good
idea to test the seeds if the packages have been opened or if
the date on the package is more than 2 years old. Plant five of
each kind of seed in separate planter cups with soil according
to the instructions in each folio. You should get 80% germination.
If you get less than four seeds of any kind sprouting, order new
seeds.
Ordering seeds. All seeds are packaged in quantities
for two class uses. To order more seeds, refer to the FOSS replacement-part
catalog. If you wish to purchase seeds locally, get seeds that
have not been treated with chemicals (such as a fungicide). Treated
seeds often have a pink powder on them.
If your students become interested in seeds and want to branch
out, go to a nursery and look over the array of seeds. You will
be amazed at what is available. Here are a couple of things to
look for.
- Seek out fairly large seeds. They are easier to handle and
count.
- Make sure that the seeds have not been treated with poison.
It guarantees sprouting but could be hazardous if handled improperly.
- Check to see how long it takes for the seeds to sprout and
for a complete life cycle.
- Check the supermarket for seeds to sprout. Grains, nuts, and
beans are all seeds.
What to do with the plants when the investigation is
completed. One word of caution involves
the attitude that students will have toward their plants. They
will probably become very attached to their plants after caring
for them for many days. In each activity it is necessary to sacrifice
the plants to look at roots or weigh the products. Be prepared.
Offer students the opportunity to replant and take the plants
home. Or have them set up extras at the start—some to keep
and some to study. It is an opportunity to have discussions about
respect for life and care for all living things.
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